Cutting head for production of ceramic parts

ABSTRACT

A tool for cutting soft pliable materials which have thixotropic properties like that of clay or raw ceramic materials. The tool includes a cutting member which has a cutting edge and a side which has an extremely short material-engaging side portion facing the severed surface of the body of the material which is to form the finished article involved (as distinguished from the shavings or pieces of waste material). The short materialengaging side portion of the tool is most advantageously formed by machining the cutting edge at an angle so the side thereof referred to slopes away from the severed surface of the material being cut. Thus, an insignificant portion of the cutting edge contacts the useful severed surface of the material being cut which avoids smearing, flowing and/or deforming of the material being cut. Most advantageously a resilient support surface is provided for receiving the material to be cut and to provide a flexible contact surface for the cutting edge of the cutting tool.

:1; ite its iet Kinney [54] CUTTING HEAD FOR PRODUCTION 01F CERAMIC lPATS [72] Inventor: Freas C. Kinney, Edison, NJ. [73] Assignee: Gulton Industries, Metuchen, NJ. [22] Filed: Dec. 30, 1968 [21] App1.No.: 787,858

[52] US. Cl 83/124 [51] Int. Cl .B26d 1/26 [58] Field ofSearch ..25/105, 106, 107, 109; 83/124,

[ 1 Jan. 18, 1972 Attorney-Wallenstein, Spangenberg, Hattis & Strampel [57] ABSTRACT A tool for cutting soft pliable materials which have thixotropic properties like that of clay or raw ceramic materials. The tool includes a cutting member which has a cutting edge and a side which has an extremely short material-engaging side portion facing the severed surface of the body of the material which is to form the finished article involved (as distinguished from the shavings or pieces of waste material). The short material-engaging side portion of the tool is most advantageously formed by machining the cutting edge at an angle so the side thereof referred to slopes away from the severed surface of the material being cut. Thus, an insignificant portion of the cutting edge contacts the useful severed surface of the material being cut which avoids smearing, flowing and/or deforming of the material being cut. Most advantageously a resilient support surface is provided for receiving the material to be cut and to provide a flexible contact surface for the cutting edge of the cutting tool.

4 Claims, 10 Drawing Figures PATENTED JMUB I972- SHEET 1 [1F 2 &

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Mam/1 CUTTING HEAD FOR PRODUCTION OF CERAMIC PARTS This invention relates generally to cutting tools, and more particularly to cutting tools for cutting soft pliable materials which have thixotropic properties.

Heretofore, there has been much difficulty in cutting materials having thixotropic properties such as clay or raw ceramic or the like without causing smearing or flowing of the material along the just-cut edge thereof due to the action of the sidewall surface of the cutting knife remaining in continuous wiping contact therewith during the linear cutting motion of the knife. Therefore, materials such as raw ceramic are usually cut to an approximate dimension and thereafter fired and cured so as to harden the material and thereafter the hardened material is machined by cutting or grinding to shape the ceramic parts to the desired predetermined dimension. This method is time consuming and expensive in that it requires extra steps to manufacture a finished part as well as requiring skilled labor for the machining operations thereof.

The disadvantages of prior art methods and apparatus for cutting and forming parts from raw ceramic materials have been particularly troublesome in the field of manufacturing ceramic layer capacitors. Heretofore, ceramic layer capacitors were made by providing conductive layers or coatings of platinum or the like between layers of raw ceramic material and thereafter cutting small disk-shaped or donut-shaped parts from the laminate structure. Some of these conductive layers or coatings extend to the outer margins and some of these conductive layers or coatings extend to the inner margins of the capacitor parts. These two groups of conductive layers or coatings are, after the raw capacitor parts are fired, respectively electrically connected together, for example, by applying inner and outer electrically conductive annular coatings. Due to the construction of the cutting knives used to cut the raw ceramic material, the severed edge surfaces of each part becomes smeared and so, in the prior art, these edge surfaces had to be cleaned to provide well-defined edges of the conductive layers. Accordingly, it was the practice in the initial cutting operation to cut the parts oversized. The over sized parts are then cured, for example, by firing, and then the cured parts are subjected to a machining operation to produce the desired well-defined edge surfaces of the conductive layers so they may be connected together to form the capacitor. Also, these techniques for making ceramic parts as described frequently caused damage to the ceramic parts resulting in a high spoilage rate.

In view of the foregoing problems encountered in tools for cutting laminate structures of materials having thixotropic properties, it is an object of this invention to provide a cutting tool which overcomes these problems.

Another object of this invention is to provide a cutting tool for cutting materials having thixotropic properties without smearing or deforming the just-cut edge of the usable portion of the material being cut.

Still another object of this invention is to provide a cutting tool for forming circular disk-shaped or donut-shaped configurations from laminates of raw ceramic materials without damaging the same.

Briefly, the cutting tool of this invention provides an improved cutting knife for cutting soft pliable materials which have thixotropic properties such as clay or raw ceramic materials. The tool include a cutting member which has a cutting edge with an exceedingly small material-engaging surface most advantageously formed by providing the tool with a slanting sidewall surface facing the surface of the useful article being cut from the larger piece of material involved. Thus, during linear motions of the cutting knife only the immediate cutting edge or a very small region thereof contacts the justcut edge of the usable portion of the material while the sidewall surface of the cutting knife is spaced from and progressively slopes away divergingly from the cutting region of the knife to be free of contact withthejust-cut edge of the material being cut. The cutting knife is thus uniquely designed to prevent smearing, flowing and/or deforming the edge regions or severed surface of the material being cut. the result being a well-defined cut edge requiring no further selected machining or grinding thereon when the tool of the invention is used to sever a raw ceramic body having alternate conductive and ceramic layers. The tool makes such a clean, nonsmearing cut that the exceedingly thin edges of the conductive layers at the severed surface of the body are exposed, well defined and undeformed. Multiple cutting knives may be provided to simultaneously cut two or more edges, as for example, the inner and outer diameters of annular-shaped ceramic disks of multiplate capacitors.

These multiple cutting knives are most advantageously maintained substantially in the same plane simultaneously to contact the top surface of the laminate body being cut and to pass through the successive layers substantially simultaneously one by one, so the laminate body is not axially or radially deformed during this cutting operation. To maintain the sheet of laminate layers in precise location during the cutting thereof, in the most desirable form of the invention, a holding member is provided having a bottom surface corresponding to the cross section of the article being formed. The holding member is closely surrounded by the relatively movable outer cutting knife and the inner cutting knife protrudes through a hole in the center of the holding member and is movable 'downwardly therethrough. When the cutting apparatus is moved into position for cutting, the holding member moves downward and engages the top surface of the laminate body and thereafter the cutting knives move relative to the holding member to engage and cut the laminate layers.

Another feature of the most preferred or advantageous form of the invention is the provision of a resilient support surface for receiving the material to be cut and to provide a flexible contact surface for the cutting edge of the cutting knife or knives when the knives cut all the way through the material being cut.

The above and other objects, advantages and features of this invention will be more fully realized and understood from the following detailed description when taken in conjunction with the accompanying drawings wherein like reference numerals throughout the various views of the drawings are intended to designate similar elements or components.

FIG. I is a perspective view of a portion of a laminate body of sheets of raw ceramic material with aligned conductive areas coated on the various layers in a pattern permitting individual donut-shaped multilayered capacitor elements to be cut therefrom by the apparatus of this invention.

FIG. 2 is a top view of a portion of one of the inner sheets of ceramic material in FIG. 1 with a circular area of conductive material deposited therein to form an electrode extending to the outer margin of a capacitor element out along the broken line indicated thereon which is of a lesser diameter than the diameter or the conductive area;

FIG. 3 illustrates a view of the portion of another sheet of ceramic material in FIG. I with a circular area of conductive material deposited thereon to form an electrode extending to the inner margin of a capacitor clement out along the broken line indicated thereon which is of greater diameter than the diameter of the conductive area;

FIG. 4 is an exploded view of some of the layers of a capacitor cut from the laminate body of FIG. I by a single stroke of the apparatus of this invention;

FIG. 5 is a perspective view of the capacitor of FIG. 4 in its completed form after firing and application of electroding thereon which interconnects the conductive areas of the capacitor layers extending to the inner and outer margins of the capacitor;

FIG. 6 is a sectional view taken along line 6-6 of the capacitor of FIG. 5;

FIG. 7 is a much enlarged elevational sectional view illustrating the major components of the apparatus of this inventron;

FIG. 8 is an enlarged sectional view of the cutting knives used in the apparatus of FIG. 7; and

FIGS. 9 and 10 are still further enlarged views showing the cutting edges and sloping walls of the cutting knives of this invention.

For an understanding and appreciation of one of the most important applications of the present invention namely in the fabrication of circular multilayer capacitors, reference is first made of FIGS. 1-4 which illustrates the manner in which the layers of raw ceramic material forming capacitors are made ready for firing when using the unique cutting apparatus of the invention. In FIG. 1 there is shown a fragmentary portion of a relatively large laminate body 10 formed by a plurality of layers 12 preferably of raw ceramic capacitor dielectric-forming material and having, deposited on all but the uppermost layer 12 of ceramic material, spaced groups of aligned circular conductive areas 14 and 16 (FIGS. 2-4), preferably of platinum paste or the like fonning the plates of a capacitor. The conductive areas 14 are continuous throughout, whereas conductive areas 16 have central openings 18 for reasons to be explained. The conductive areas 14 have a lesser diameter than the diameter 17 of conductive areas 16. The opening 18 in each conductive area 16 is larger than the hole 19 indicated by a broken line which is to be cut through the laminate body by the cutting apparatus of the invention shown in FIGS. 7-10. The outer diameter cut by the apparatus of the invention is indicated by the broken line 21 and is ofa lesser diameter than the major diameters of the conductive areas 16 to ensure that the conductive material of the areas 16 are exposed entirely about the periphery thereof after the cutting operation and thereafter can be electrically enterconnected at their edges. On the other hand, the inner diameters 19 are less than the diameter of the openings 18 to ensure that none of the conductive material of the areas 16 will be exposed along the inner surface of the aperture defined by the inner diameter 19. However, the outer diameter 21 is greater than the major diameter of the areas 14 so that none of the peripheral edges thereof will be exposed during the cutting operation. Since the conductive areas 14 are continuous, the inner diameter 19 formed by the cutting apparatus will expose successive alternate layers of the inner edges of the areas 14 which are thereafter electrically interconnected at these edges to form the multilayer capacitor. Therefore, of the alternate groups of conductive areas 14 and 16, the outer edges of the areas 16 are exposed while the inner edges of the areas 14 are exposed during the cutting operation, therefore, requiring no further machining or grinding.

As seen in FIG. 1, a plurality of capacitor stacks 22 are formed in the laminate body 10 with the top sheet 12 thereof having visual indexing markings thereon, as indicated by the broken lines 23, to facilitate visual manual positioning of each of the capacitor stacks 22 in registry with the cutting knives of this invention for cutting capacitors from the laminate body 10. That is, the operator can position the outline 23 underneath the cutters and manually or automatically operate the cutting apparatus to move the cutting knives downward and cut the capacitor stacks 22 in substantially the approximate location indicated by the outline 23.

After the capacitor stacks 22 are cut they are cured or fired in a conventional manner well known in the art, and thereafter require no further machining operation since the severed edge surface of the capacitor stack is well defined exposing the appropriate layers of conductive material. After the capacitor stacks are cured the peripheral inner and outer portions thereof are provided with conductive coatings to connect together the respective alternate plates of the capacitor. This is best seen in FIGS. 5 and 6 wherein the capacitor stack 22 is provided with an inner conductive coating 24 which electrically connects together the inner edges of the areas 14 and an outer conductive coating 26 which electrically connects together the outer edges of the areas 16, the conductive coating 24 and 26 being formed preferably of a conductive platinum paste or the like which is capable of air curing at atmospheric pressure or which may be cured or set by application of heat, it being understood that the conductive coatings 24 and 26 may be applied before or after the curing of the capacitor stacks 22. The annular conductive coatings 24 and 26 are then electrically connected to suitable leads for connection in an electronic circuit. This may be accomplished by terminating ends of the leads in pressure contact with the coatings 24 and 26 and which are encapsulated by suitable encapsulating methods.

Referring now to FIG. 7 there is shown an elevation sectional view of a cutting tool which is constructed in accordance with this invention and is designated generally by reference numeral 30 and comprises, among other things, a housing 31 for carrying a pair of cutting knives 32 and 34, drive means 36 to effect manual or automatic linear movement of the housing 31 and cutting knives 32 and 34 toward and away from the laminate body 10, and a resilient support surface 38 for receiving and supporting the laminate body 10 during the cutting operation. The housing 31 includes a detachable end wall 42 through which the cutting knives 32 and 34 extend. The cutting knife 34 is secured to the end wall 42 by suitable means, such as bolts 44, to fix the cutting knife 34 to the end wall. The cutting knife 32, however, is adjustably secured to the housing 31 by means of a threaded shaft 46 extending from and part of the cutting knife 32, and a locking nut 48 is threadily attached to the shaft and engages the housing 31 to lock and prevent further movement of the hollow shaft 46. Therefore, the cutting knife 32, connected to or part of the shaft 46, is adjustable up and down relative to the cutting knife 34 thereby enabling positioning of the cutting edges of the knives in the same plane so that both the inner and outer diameter of the capacitor stacks 22 are cut completely through the laminate body 10 during one linear movement of the cutting head 30. Although the cutting knife 32 is shown as the adjustable knife it will be understood that either or both of the knives may be adjustable to enable positioning of the cutting edges in the same plane.

To hold the laminate body 10 in position beneath the cutting knife during the cutting operation, a holding member 50 is provided and has an aperture or passage 51 for receiving the cutting knife 32 through the center thereof. The holding member 50 is embraced by the cutting knife 34, as seen on the drawings, and the holding member 50 extends axially beyond the cutting edges of the cutting knives 32 and 34 and the end surface of the holding member is the first thing to engage the top surface of the laminate body 10. The holding member 50 includes a flange or head 52 which extends radially outwardly at the top end thereof to overlie the upper end of the cutting knife 34 and receives a coil spring 54 for applying sufi'lcient pressure to the holding member to cause holding of the laminate body 10, at least in the region being cut, while not deforming the layers 12 or 12 of the laminate body 10. Therefore, as the cutting head 30 moves downward toward the body 10, the holding member 50 is slightly displaced, as indicated by the spacing between the flange 52 and the upper end of the knife 34, and thereafter the holding member remains substantially fixed in position applying sufficient holding pressure while the cutting knives 32 and 34 and the remainder of the housing 31 move relatively thereto to cause cutting of the body 10. Upon reverse movement of the cutting head 30 the cutting knives together with the holding member 50 move upward and the cutting knife 32 again retracts within the holding member 50 while the cutting knife 34 is again positioned embracing the holding sleeve, the holding member remaining in contact with the top surface of the body 10 until the flange 52 engages the upper portion of the knife 34. The relative dimensions between the cutting knives 32 and 34 and the corresponding cylindrical surfaces of the holding member 50 immediately adjacent the cutting edges of the cutting knives may be relatively small so as to provide a wiping or cleaning action of the cutting edges as the knives move within and about the member 50 respectively. Another advantage of the holding member 50 is that the relative dimensions between the cylindrical surfaces of the member 50 and the cutting knives 32 and 34 are maintained at a value such that a slight rubbing action occurs between the surfaces of the holding member50 and the cutting edges of the cutters 32 and 34 so the cutting edges are sharpened by-this slight wiping action. Furthermore, the holding member 50 functions to protect the cutting edges of the cutting knives since these edges are very thin in cross section and, therefore, easily damaged.

Referring now to FIG. 8 there is shown an enlarged sec tional view of the cutting portion of the cutting knives 32 and 34 engaging a portion of the laminate body 10. After the cutting knives 32 and 34 pass through the laminate body to form the capacitor stack 22, the cutting knives 32 and 34 are retraced upwardly and the portion 22a, of the capacitor stock 22, remaining within the inner cutting knife 32 may be dislodged from its wedged position by a fixed rod 56 which extends through the hollow shaft 46 for this purpose.

FIG. 9 illustrates an enlarged sectional view of a portion of the cutting knife 32 extending into laminate body 10 to cut out the unused portion 22a of the capacitor stack 22. Here it is seen that the cutting edge 32a of the cutting knife 32 is fonned of a very thin wall segment 32b which has an approximate thickness of 0.0005 inch, at the region of the cutting edge 32a with increasing thickness in the direction away from the cutting edge, it being understood that this dimension and all other dimensions set forth herein are exemplary. As the cutting edge 32a passes through the body 10 it forms a well defined severed edge surface 22b free of smearing or deforming of the laminate layers of raw ceramic to expose at this surface the inner portions of the conductive areas 14. Preferably outer wall surface 32c of the cutting knife 32 divergingly slopes away from the severed edge surface 22b to define a very small material-engaging portion 32d which extends axially but a fractional distance of the thickness of one layer 12. The material-engaging portion 32d is preferably formed by a small portion of the sidewall 32; which is machined parallel to the severed edge surface 22b an axial extent of approximately 0.005 inch and from this dimension the wall 320 slopes away from the severed edge 22b and is spaced therefrom an axial extent at least equal to the total thickness of the laminate body 10, it being understood that the wall surface 32c may have configurations other than sloping so long as no part thereof other than the material-engaging portion 32d comes in contact with the severed edge 22b. Therefore, only a very small portion of the wall surface 320 of the cutting knife 32, engages the severed edges surface 22b both on the cutting stroke and the retracting stroke of the knife thereby substantially eliminating smearing of the layers 12 so as not to cover the edges of the conductive areas 14.

FIG. 10 is an enlarged sectional view of a portion of the cutting knife 34 and illustrates a cutting edge 34a extending through the laminate body 10 and further illustrates the severed edge surface 220 the capacitor stack 22 which defines the outer diameter of the capacitor stack. The inner peripheral wall surface 34b of the cutting knife 34 divergingly slopes away from the severed edge surface 220 so as to be spaced therefrom except in a small region defined by the material-engaging portion 34c which extends axially a very small distance which is a fraction of the thickness of one layer 12 of the laminate body 10. [n this instance, the wall surface 34b starts sloping substantially immediately adjacent the cutting edge 34a, it being understood that the wall surface 34b may have configurations other than sloping so long as no part thereof other than the material-engaging portion 1340 comes in contact with the severed edge 220. Accordingly, both cutting knives 32 and 34 provide cutting edges whereby only small portions thereof engage the severed edge surface of the usable portion of the material being cut while the sidewalls of the cutting knives facing the severed edges slope away to prevent wiping or smearing of the raw ceramic material forming the laminate layers of the body 10.

Throughout the specification and claims the term material having thixotropic properties" is intended to mean such material which have a tendency to smear or flow as a result of cutting or shearin forces ap lied thereto. I

In view of the oregoing etailed description it Wlll be understood that variations and modifications may be effected without departing from the spirit and scope of the novel concepts of this invention.

lclaim:

l. A cutting tool for cutting materials having thixotropic properties to divide the material into usable portions and waste portions, comprising: a housing capable of linear movement toward and away from the material being cut; movement means connected to said housing to effect movement thereof; a first cylindrical cutting knife secured to said housing and movable therewith for cutting an outer diameter of a circular part being cut from the material, said first cylindrical cutting knife having a cutting edge to engage and cut the material to form a first severed surface on the usable portion of the material being cut and further having a slanted wall opposite said first severed surface and diverging from said first severed surface and spaced therefrom at all regions except for a finite material-engaging portion thereof which is a fraction of the thickness of the material being cut; a second cylindrical cutting knife secured to said housing and movable therewith and positioned concentrally within said first cylindrical cutting knife for cutting an inner diameter within the circular part being cut from the material, said second cylindrical cutting knife having a cutting edge which is substantially in the same plane as said cutting edge of said first cylindrical cutting knife to cut the material to form a second severed surface on the usable portion of the material being cut and a slanted wall opposite said second severed surface and diverging so as to be spaced therefrom at all regions except for a finite material-engaging portion thereof which is a fraction of the thickness of the material being cut; and a support surface located beneath said housing and spaced from said first and second cylindrical cutting knives to receive and support the material being cut.

2. A cutting tool according to claim 1 wherein one of said first and second cylindrical cutting knives is adjustable for alignment with respect to the other of said first and second cylindrical cutting knives for positioning the cutting edges of said cutting knives in substantially the same plane.

3. A cutting tool according to claim 1 further including a holding member circumferentially positioned between said first and second cylindrical cutting knives and extending axially beyond the cutting edges thereof when the housing is in the retract noncutting position, said holding member being resiliently biased toward the top surface of the material being cut and axially movable relative to said first and second cutting knives when said housing is moved toward the material being cut and the holding member engages said top surface whereupon the holding member remains at said top surface while said first and second cutting knives continue their linear movement through the material to cut the material.

4. A cutting tool according to claim 3 wherein said holding member is dimensioned to be closely spaced with respect to the cutting edges of said first and second cylindrical cutting knives to provide a wiping surface for the respective materialengaging portions of the inner and outer cutting knives when the cutting knives are retracted to their noncutting position. 

1. A cutting tool for cutting materials having thixotropic properties to divide the material into usable portions and waste portions, comprising: a housing capable of linear movement toward and away from the material being cut; movement means connected to said housing to effect movement thereof; a first cylindrical cutting knife secured to said housing and movable therewith for cutting an outer diameter of a circular part being cut from the material, said first cylindrical cutting knife having a cutting edge to engage and cut the material to form a first severed surface on the usable portion of the material being cut and further having a slanted wall opposite said first severed surface and diverging from said first severed surface and spaced therefrom at all regions except for a finite material-engaging portion thereof which is a fraction of the thickness of the material being cut; a second cylindrical cutting knife secured to said housing and movable therewith and positioned concentrally within said first cylindrical cutting knife for cutting an inner diameter within the circular part being cut from the material, said second cylindrical cutting knife having a cutting edge which is substantially in the same plane as said cutting edge of said first cylindrical cutting knife to cut the material to form a second severed surface on the usable portion of the material being cut and a slanted wall opposite said second severed surface and diverging so as to be spaced therefrom at all regions except for a finite material-engaging portion thereof which is a fraction of the thickness of the material being cut; and a support surface located beneath said housing and spaced from said first and second cylindrical cutting knives to receive and support the material being cut.
 2. A cutting tool according to claim 1 wherein one of said first and second cylindrical cutting knives is adjustable for alignment with respect to the other of said first and second cylindrical cutting knives for positioning the cutting edges of said cutting knives in substantially the same plane.
 3. A cutting tool according to claim 1 further including a holding member circumferentially positioned between said first and second cylindrical cutting knives and extending axially beyond the cutting edges thereof when the housing is in the retract noncutting position, said holding member being resiliently biased toward the top surface of the material being cut and axially movable relative to said first and second cutting knives when said housing is moved toward the material being cut and the holding member engages said top surface whereupon the holding member remains at said top surface while said first and second cutting knives continue their linear movement through the material to cut the material.
 4. A cutting tool according to claim 3 wherein said holding member is dimensioned to be closely spaced with respect to the cutting edges of said first and second cylindrical cutting knives to provide a wiping surface for the respective material-engaging portions of the inner and outer cutting knives when the cutting knives are retracted to their noncutting position. 